Mr Phillips-Davies, who was appointed deputy chief executive last year, joined Southern Electric, SSE’s predecessor, in 1997 before becoming energy supply director in 2002.

He will be supported by finance director Gregor Alexander, whose role is being expanded to include deputising for the new chief executive.

Mr Marchant, one of the longest-serving bosses of the Big Six energy companies, did not give details about his plans but insisted he did not want “another big executive job”.

He was described by SSE chairman Lord Smith of Kelvin as a “chief executive of the highest standard”.

“In every one of his years as chief executive, SSE has delivered above-inflation increases in the dividend while making significant progress throughout its operations, including the quality of service provided to network and retail customers, and in other key areas such as the development of renewable energy.”